MBSR teacher (well, learning!) here. I would also be skeptical based purely on the sample size, but MBSR as a treatment is pretty well researched and documented. It's been around for 40+ years and there is fairly extensive supporting research [1].

So - I wouldn't be in any way surprised if there are other related treatments which have high levels of efficacy...

[1] https://en.wikipedia.org/wiki/Mindfulness-based_stress_reduc...